Our only hope of escaping these dangers, says Hawking, is by finding another habitable planet.

"We must also continue to go into space for the future of humanity," he said. "I don’t think we will survive another 1,000 years without escaping beyond our fragile planet."

NASA launched its Kepler spacecraft in 2009, whose mission is to do just that. It was designed to search the nearby region of our galaxy for Earth-sized planets orbiting in the habitable zone of stars similar to our sun. This zone is also called the "Goldilocks zone" because it is the range where pressure and temperature are "just right" for liquid water to exist on a planet's surface.

This year, the astronomers were excited by the discovery of Proxima B, which is an Earth-size planet orbiting in the star Proxima Centauri's habitable zone. It also lies just 4.2 lighty-ears away from us, which in space terms is pretty close. So far, Proxima B looks like our best chance of escape.

Hawking's speech ended with him encouraging the students to stay curious and told them to remember to "look up to the stars and not down at your feet."